LuduminaAT-08 · AT-U3 · Planned
Fission and controlled chain reactions
Learning objectives
Explain induced fission, neutron release and chain reactions; identify control roles and energy transfers.
8463 §§4.4.4.1 / No Trilogy counterpart
DfE single-science pp.43–44 / Combined pp.35–36. Evidence checked 30 September–1 October 2026. Skills: WS1.2,1.4,3.6.
Explanation
Fission of a heavy nucleus releases smaller nuclei, neutrons and energy. Some released neutrons can cause further fissions, giving a chain reaction. Absorbing enough neutrons controls the branching rate; the energy comes from nuclear changes rather than fuel combustion.
Concepts, equations and units: Heavy nucleus splits into two smaller nuclei plus neutrons and radiation; kinetic energy of products; control rods absorb neutrons; no mass-energy equation required.
Prediction, demonstration and game exercise
Predict, observe, explain
Show probabilistic neutron branching with controllable absorption; distinguish controlled reactor and uncontrolled chain reaction.
Planned learner game exercise
Adjust model neutron absorption to maintain a stated reaction rate and explain resulting energy ledger.
Independent practice
Label a reaction diagram and write a four-step chain/control explanation.
Original practice example · Separate Physics
Explain how absorbing neutrons changes a chain reaction.
Show working and model answer
Working / reasoning
Fewer emitted neutrons are available to induce subsequent fissions, reducing the number of new events.
Answer
It reduces subsequent fission events and can control the reaction rate.
Exit check and success criteria
Correct initiating neutron, products and subsequent-neutron chain; control explanation conserves energy.
During practice, compare the prediction with evidence and give an error-specific prompt. The exit item uses a fresh context or fresh values, answered independently.
Misconceptions, practical links and mastery
Check these misconceptions
Fission is burning; rods supply extra neutrons; every emitted neutron causes another fission.
Practical preparation
No RP; abstract model, no reactor-operation instructions.
Virtual preparation and revision only. Required hands-on activities and school records remain separate.
Proposed mastery
0: not yet evidenced. 1: supported. 2: independent exit criteria met. 3: successful changed-context transfer. Advance at 2; revisit with fresh retrieval. These are not GCSE grades.